Various types of ultrasonic devices are used for surgical applications, for example, ophthalmological surgery for removing cataracts and other tissue. These devices employ a hollow work tip to transmit the ultrasonic energy which emulsifies the tissue to be removed. Such tips are typically made of titanium and usually have about 0.5 to about a 1 mm outside diameter and about a 0.6 to about 0.9 mm inner diameter.
In U.S. Pat. No. 5,242,385, an ultrasonic handpiece which is also capable of supplying an irrigation fluid to the operating site is described, with suction used for removing the material which has been emulsified by the ultrasonic transducer. A work tip is described which has an enlarged hollow front end forming a cavity into which the material to be emulsified is drawn and within which the material is emulsified. However, while the cavity promotes emulsification, the narrowing of the passage adjacent to the cavity creates a potential location for blockage of the tip to occur.
In U.S. Pat. No. 5,213,569, an ultrasonic phacoemulsification tip is described which has a rounded edge to prevent eye tissue damage, using an increased wall thickness, and to use a concave recess in the end face. The purpose is to more closely align the tip geometry for more effective utilization of the ultrasonic energy. However, this again results in a necking down in the tip which again can result in blockage.